Heating device



2 Sheets-Sheet 1 INVENTOR.

W fli A T TORNE' VS LESTER l/ JORGENSE/V L. V. JORGENSEN HEATING DEVICEJan. 5, 1960 Filed Oct. 28, 195'? Jan. 5, 1960 v, JORGENSEN 2,920,176

HEATING DEVICE Filed Ogt. 28. 1957 2 Sheets-Sheet 2 Q n N N gg-aa/uVdJdI IGLL MOJ INVENTOR. LESTER MJORGENSEN ATTORNEYS States PatentHEATING DEVICE Application October 28, 1957, Serial No. 692,887

, 7 Claims. (Cl. '21919) This invention relates to an improvement inapparatus for treating filamentary material and more particularly to adevice for supplying heat to a filamentary material containing filamentscomposed of a synthetic material such as that formed from acrylonitrilepolymers and the like during a textile operation so as to bring thematerial to a predetermined state of plasticity and facilitate thestretching or drafting of the filaments in the material. ;In manytextile operations, particularly those operationswhere a continuousfilamentary tow of synthetic material is treated, it is a commonpractice to stretch or elongate the filaments in the tow in order toimpart certain desirable qualities to the filaments such as increasingtheir tensile strength. This stretching operation is generally carriedout by applying heat to the filaments so as to raise their temperatureto the level at which the tow is in a sufliciently plastic state tofacilitate stretching. In one type of textile operation with which thisinvention is particularly concerned and which incorporates aheatstretching' step theoperation is carried out on a tow of continuousfilaments to convert the continuous filaments to fibers of relativelyshort length. A machine for carrying out this conversion operation isreadily available commercially and is commonly known in the textileindustry as a turboconverter or turbostapler. One such machine is shownin Patent No. 2,748,426, issued to W. K. Wyatt .on June 5, 195 6, andthis invention is particularly directed -to an improvement on thismachine.

A turboconverter such as that described in the Wyatt patent incorporatesa heat-stretching step during which the'laterally spread filamentary towadvances between heated plates or platens which heat the filaments sothat they can be stretched a predetermined amount between two pairs ofnip rolls rotated at different speeds.

it was found in the processing of synthetic textile material, 'forexample filaments formed from acrylonitrile polymers, that yarnprocessed in such a turboconverter wascharacterized by an excessiveamount ofrelatively short lengths of filaments which were freelydistributed in the yarn or what is known inthe industry as fly. This flyappeared in such quantities in fabric forming textile operationssubsequent to conversion such as knitting as to greatly exceed thecommercially acceptable limit. As is well known, when the fly isexcessive in processed yarn, .the fly which is not carried in the airand deposited on the apparatus to interfere with proper operationremains entwined in the fabric to give it an unsatisfactory surfaceappearance. Furthermore, the stretched tow did not emerge from betweenthe platens in a substantially unbroken form as filament breakageappeared to occur to a large degree during the heat-stretchingoperation. I I

Subsequent investigation and study revealed the startling fact that theheat supplied to the tow and the temperature to which the tow was raisedduring application of heat were extremely critical and the constructionand operation of the prior heating plates in the turboconverter wascreating the unsatisfactory condition of 7 Ice excessive fly andfilament breakage during heatstretching. Temperature distributionthroughout the plates was not uniformly controlled and cold spots werefrequent, creating highly improper heating of a filamentary tow composedof the above materials.

Accordingly, a primary object of this invention is to provide a new andnovel device for heating filamentary material so as to bring thefilaments uniformly to a plastic state in which they may be readilystretched.

Another object of this invention is to provide a new and novel heatingdevice for heating a tow of synthetic material comprising continuoustextile filaments formed from acrylonitrile polymers and the like whichenables the filaments to be brought quickly to a predetermind stretchingtemperature throughout an extended length of tow and which maintainssuch temperature within the continuously advancing tow so as to permitstretching of the filaments to be continuously accomplished in a highlysatisfactory, substantially uniform manner.

A further object of this invention is to provide a new and improvedheating device for the heat-stretching step in turboconverter apparatusof the type for converting continuous filament tow to staple fiber tow.Still another object of this invention is to provide a new and novelheating device for supplying heat to filamentary tow formed from suchsynthetic material as acrylonitrile polymers which substantially reducesfly in the subsequent processing of yarn containing the heat-stretchedfilaments and which substantially eliminates filament breakage duringthe heat-stretching operation.

In the processing of filaments with a turboconverter of theabove-described type, attempts to alter the results obtained in the endproduct by changing conditions such as platen temperature, tow advancingspeed, and the like, gave widely diverse results which defiedprediction. It is well known that synthetic materials such as those fromwhich the above filaments were formed are very sensitive to heattransfer conditions and further difficulty was experienced with thelimited control ofiered in the previous heating plates as the heatingconditions at the plates could not be established with the degree ofaccuracy and pattern of temperature distribution necessary for thedesired filament heat treatment. Furthermore, in the previous design ofthe heating platens, warping of the platens created a substantial lackof uniformity in platen spacing throughout the opposed heating surfacesparticularly when the platens were hot, adding further to the lack ofheat transfer control. Consequently, yarn physical characteristics couldbe controlled only to a very limited extent at best.

A still further object of this invention is to provide a new and novelheating device for facilitating the heatstretching operation performedon filamentary tow which makes it possible to tailor the yarn endproduct physical character to the customer's specifications by changingthe temperature at the heating device while maintaining the level of flysubstantially below the commercially acceptable limit.

Still another object of this invention is to provide a new and improvedheating device for facilitating the stretching of filamentary towcomposed of synthetic material such as acrylonitrile polymers or thelike which utilizes spaced heating platens, the spacing of which ismaintained substantially uniform throughout under all conditions oftemperature.

This invention further contemplates the provision of a new and improvedheating device for facilitating the stretching of a filamentary towformed from synthetic material such as acrylonitrile polymers or thelike which is particularly adapted for use in the heat stretchingsection of a turboconverter or turbostapler to uniformly bring thecontinuously moving, laterally spread tow to any predetermined softeningtemperature selected in accordance with the yarn physicalcharacteristics desired and maintain an extended length of tow in theheating device at such temperature so that filament stretching isaccomplished in the desired manner with reduced filament breakage and arelatively low level of fly while producing an end product of accuratelycontrolled physical characteristics.

Other objects and advantages of the invention will become apparent fromthe following description taken in connection with the accompanyingdrawings.

In general, the objects of the invention are accomplished by providing apair of substantially parallel platens each of which contains a heattransfer surface arranged in opposed relationship. A continuous rope ortow of filamentary material such as filaments formed from acrylonitrilepolymers or the like is arranged to move between the opposed surfaces ofthe platens in heat transfer relationship therewith. The platens areheated internally by a plurality of heating means which extendsubstantially transverse or at 90 degrees to the direction of towmovement and heating means of predetermined capacity are spaced alongthe platens in the direction of tow movement so that the tow heating maybe obtained in a pre determined pattern along the portion of the towlying within the platens. Means are provided for sensing the temperatureof the platen heating surfaces and for controlling the operation of theplaten heating means so that relatively cold tow entering the platens isquickly brought to a predetermined stretching temperature and softenedand a predetermined length of tow within the platens is maintained atthis temperature during tow advance to permit stretching of the towunder conditions whereat fly is held to a low level.

The novel features which are believed to be characteristic of theinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method ofoperation may be best understood by reference to the followingdescription taken in conjunction with the accompanying drawing in which:

Figure 1 is a diagrammatic view of an apparatus for processingfilamentary tow commonly referred to as a turboconverter of which thisinvention is an improvement;

Figure 2 is an enlarged perspective view of the heating device of theinvention incorporated in the apparatus of Figure 1;

Figure 3 is a sectional view taken substantially along line 3-3 ofFigure 2; and

Figure 4 is a typical graph of the temperature distribution along thatportion of the filamentary tow extending within the heating device ofFigure 2.

Referring now to Figure 1, there is shown diagrammatically an apparatuscommonly referred to in the textile industry as a turboconverter or aturbostapler. As is well known, the turboconverter is employed toconvert a bundle of continuous filaments to fibers of staple length witha breaking operation and may be of the type disclosed in the Patent No.2,748,426 issued to W. K. Wyatt on June 5, 1956. Although the instantinvention may be employed in a variety of textile applications, itrepresents in particular an improvement on a turboconverter of the typeshown in the Wyatt patent and it will be described hereinafter as such.

As described in the above-mentioned patent, a fila mentary tow 11advancing through the apparatus initially threads between successivesnubber bars 12 and enters a pair of rubber sheathed nip rolls 13, 14.From the nip rolls 13, 14, the tow 11 moves around a first set ofauxiliary rolls 15 and travels through a heating device designatedgenerally by the numeral 16 and comprising a pair of heated plates orplatens 17, 18. It should be understood that this invention lies in thespecific construction of the heating device 16 and is therefore to bedistinguished from the heating device of the Wyatt patent.

Leaving the platens 17, 18, the tow 11 moves through a second set ofauxiliary rolls 19 into a second pair of rubber sheathed nip rolls 21,22. As is well understood, the tow 11 is heated and softened during itspassage between the platens 17, 18 and the nip rolls 21, 22 are operatedat a faster speed than the nip rolls 13, 14 so that the softened tow 11is stretched in any suitable ratio depending, of course, on thedifferential speed of the nip rolls 13, 14 and 21, 22. For instance, atypical stretch ratio may be 1.5/1.

From the nip rolls 21, 22 the tow 11 advances through a tow guide 23which controls the laterally spread tow and into break-up rolls 24, 26from which it is carried by cooperating delivery nip rolls 27, 28 sothat the continuous filaments are broken into fibers of staple lengthbetween the break-up and the delivery rolls. The tow then moves overguide plate 29 and around rod- 31 into a pair of cooperating nip rolls32, 33 which feed the tow into a crimping chamber or box 34 so thatcrimped staple tow is deposited into a receiver 36.

In the processing of filamentary tow composed of heat sensitivesynthetic material particularly synthetic material of the acrylic type,a turboconverter of the abovedescribed type gives an end product whichproduces fly far above the permissible commercial limit and excessivefilament breakage occurred in the heating device 16. Study andexperimentation led to the discovery that control of the temperaturedistribution and heat transfer conditions in the heating device werecritical in the opera-- tion of the turboconverter when used for theprocessing of such material.

In accordance with the novel construction of the invention, means havebeen provided for supplying heat to the filamentary tow as it enters theheating device 16 to bring it quickly and uniformly to a predeterminedsoftening temperature and maintain it at such a temperature during asubstantial portion of its traverse through the heating device so as tofacilitate stretching and reduce the fly produced to an absoluteminimum.

More specifically, as shown in Figures 2, 3 the heating means 16comprise a pair of platens 17, 18 which are supported in any suitablemanner such as that shown in the above-mentioned patent with theiropposed faces or heating surfaces 37, 38 in substantially parallelrelationship. The platens 17, 18 are arranged to be moved by means of asuitable manually operable linkage between an open or widely spacedrelationship to facilitate threading of the tow 11 therethrough to aclosed position (Fig. 3) in which the tow advances through the platensin heat transfer contact with the surfaces 37, 38.

In order to simplify the illustration of the invention the platenoperating linkages are only partially shown but it should be understoodthat an operating handle 35 is suitably connected to the platens bymeans such as a swivel bracket 39 suitably secured to the platens bymeans of straps 40 as shown on the platen 17 in Figure 2. The platen 17may be provided with a central recess 41 for accommodating a portion ofthe linkage connected to the platens. It should be understood thatplatens 17, 18 are substantially identical in construction except thatthey are of opposite hand and only platen 17, hereinafter referred to asthe upper platen, will be discussed in detail.

In order to insure that the heating surfaces 37, 38 are maintained inparallel relationship and eliminate warping of the platens, the platens17 18 are preferably composed of a material of high heat conductivitysuch as aluminum or magnesium. It can be understood that if the spacingbetween the surfaces 37, 38 is not uniform throughout. the heatingdevice 16, heat transfer between the surfaces and the tow 11 will varyaccordingly with attendant inaccuracies in the temperature controlduring the traverse of the tow through the heating device 16.

As. specifically illustrative of the novel construction of theinvention, means have been provided for supplying heat to the platens17, 18 in order to bring the tow 11 quickly and uniformly to apredetermined stretching temperature. More specifically, the upperplaten 17 is provided with a plurality of transversely extending bores42 through 47 preferably cylindrical in shape which lie at substantially90 degrees to the direction of tow movement as indicated by arrow H.Thus these cylindrical bores extend transversely in the heating device16 and arespaced suitably as shown in Figures 2, 3 along the upperplaten in the direction of tow movement. The bores 42 through 47 arearranged to accommodate heating means such as cylindrical unit heaters48 through 53 respectively also preferably cylindrical in shape so as tobe snugly accommodated within the bores. These heaters are arranged tobe connected by means such as wires 54 to any conventional type ofswitching device (not shown) which enables the heaters to be connectedto a suitable source of power.

It can be seen that with the unit heaters arranged in the novel mannerof the invention so as to extend in a 90 degree direction to themovement of the tow, the tow will be heated uniformly throughout itslateral dimension. Thus inadequate heating or cold spots in the towcharacteristic of prior heating devices, such as those with heatersextending in the direction of tow movement, are

eliminated.

Although any number of unit heaters may be employed, in the illustratedembodiment such heaters are preferably six in number and are positionedwithin platen 17 in such a manner as to define two groups each arrangedadjacent one end of the upper platen 17. Similarly, platen 18hereinafter referred to as the lower platen, is provided withtransversely extending bores 56 through 61 arranged to accommodate unitheaters 62 through 67 as shown best in Figure 3.

As is well understood, the tow 11 prior to entering the heating device16 is cold or in a virtually unheated state. Therefore, a substantialtemperature differential exists between this initial tow temperature andthe predetermined temperature to which the tow must be elevated forefficient stretching to be accomplished. Consequently,

.unit heaters 48, 49 adjacent the end of the upper platen at which thetow enters and designated hereinafter as a -rear end are of largercapacity than the remaining heaters and are accommodated within thetransverse bores 42, 43 respectively which are appropriately of largedimension as shown. Thus large quantities of heat are transferred to thetow immediately after it enters the heating device 16 to bring the towquickly to the predetermined stretching temperature at which it ismaintained by the subsequent heaters 50 through 53 spaced along theplaten. Similarly, the lower platen 18 is provided with large capacityheaters 62, 63.

Although the unit heaters employed in the heating device 16 may be ofany suitable heating capacity in accordance with the generalrequirements discussed above, in the specific embodiment illustratedheaters 48, 49 are prefertemperature for a substantial length within thedevice in order to obtain the novel results accomplished by theinvention. It should be understood, however, that although heaters oflarger capacity are employed at the rear end of the heating device 16,their output should be limited so as to preclude the scorching orburning of the tow. With the use of heaters of the capacity specifiedabove, satisfactory heating of the tow is obtained for the processing ofa wide variety of synthetic filamentary material as well as othermaterial which responds to such a heating operation.

Referring now to Fig. 4 there is shown a graphical representation of onetypical temperature distribution throughout the portion of the movingtow sandwiched between the heating platens 17, 18. For instance, whenthe platens are approximately 14 inches in length the tow is brought tothe stretching temperature in a sufficiently short period of time sothat approximately 10 inches of the tow sandwiched between the platensis maintained at the stretching temperature.

It can be seen that the tow 11 which enters the rear end of the heatingdevice 16 at substantially room temperature is rapidly heated along theplaten length and reaches the predetermined stretching temperature (230degrees F.) at a distance of approximately 4 to 5 inches past the rearend of a 14 inch length plate with the portion of the tow extendingthroughout the remaining length of the platens being maintained at thestretching temperature. This tow heating arrangement is in accordancewith one novel aspect of the invention as it was found that properfunctioning of the heating device 16 so as to give an end product ofdesired characteristics required that the stretching temperature bemaintained throughout this extended portion of the tow length sandwichedbetween the platens 17 18.

It can be understood that in order to control the temperature of theheat transfer surfaces 37, 38 on the platens 17, 18, the unit heaters 48through 53 and 62 through 67 must be operated under closely controlledconditions in order to obtain the proper temperature distribution alongthe platens as indicated by the curve of Figure 4. As heat transferbetween the surfaces 37, 38 and the tow 11 depends in the main on thetemperature differential between the surfaces and the tow, only aheating system which responds to surface temperature will give the heattransfer conditions necessary for the proper operation of the invention.Prior constructions have located the temperature sensing means remotefrom the heat transfer surfaces and consequently have given inaccuratereadings.

Any suitable type of temperature sensing means may be provided forsensing the temperature of the surfaces 37, 38 such as thermocouples orthe like suitably spaced throughout the area of the surfaces which maybe connected to suitable control devices for energizing the unit heatersin accordance with the heating requirements. However, in the specificembodiment, a somewhat simpler control and sensing system is utilizedwhich has given satisfactory performance.

More specifically, the upper platen 17 is further provided withtransverse bores 71, 72 preferably cylindrical in shape each arrangedadjacent opposite end of the upper platen 17 as shown in Figure 3. Thebores 71, 72 are arranged to snugly accommodate combined temperaturesensing and control means 73, 74 respectively, which are connected tothe heater switching means (not shown) by means such as lead wires 76.Similarly, the lower platen 18 is provided with bores 77, 78 containingcombined temperature sensing and control means 79, 81 respectively. Inthe specific embodiment illustrated each of the temperature sensing andcontrol means are connected for gang operation of the three unit heaterswith which it is associated.

The combined temperature sensing and control means employed in thespecific embodiment illustrated are therefore a commercially availabletype of controller'which acts in response to the amount of heat flowingat its location in the platen to control the operation of the unitheaters through their associated switching means and maintain apredetermined temperature at the heat transfer surface under aparticular set of tow advancing conditions such as tow speed, thicknessand the like.

It should be understood that the controllers are manually adjustable bymeans such as control knobs 82 (Fig. 2). Therefore, the desiredoperating temperature at the heat transfer surface 37 for a particularset of tow advancing conditions may be obtained by means of a pluralityof thermocouples 83, 84 positioned in wells 86, 87 respectively in theupper platen 17 adjacent each end of the platen. These thermocouples areconnected for the purpose of initial heater control adjustment by meanssuch as lead wires 83 to suitable temperature recording means (notshown). As shown in Figures 2, 3, the thermocouples at each end of theplaten are arranged in rows of 3 extending transversely of the upperplaten so as to given temperature readings at specific localities acrossthe platen. The walls 86, 87 are of such 'depth as to position the heatsensitive tip of each thermocouple closely adjacent the heat transfersurface 37. It has been found that a spacing of approximately 2 of aninch gives a satisfactorily accurate indication of surface temperature.Similarly, the lower platen 18 contains thermocouples 89, 90 positionedin wells 91, 92 which are connected by means of lead wires 93 to thetemperature recording means.

Thus a predetermined surface temperature may be established across theplatens at each bank of thermocouples by rotating the control knob oftheir associated controller to obtain the desired heater output for eachset of tow running conditions. For example, with a tow speed of 82 feetper minute entering the platens a temperature reading of 362 degrees F.at the upper and lower thermocouples 83, S9 and a temperature of 398degrees F. at upper and lower thermocouples 84, 90 gives a highlysatisfactory heat-stretching performance for a stretch temperature of210 degrees F. It should be understood that once the temperature settingis made by means of the controller no further reference to thethermocouples is necessary.

As previously discussed, other systems may be provided for controllingthe temperature conditions at the platens heat transfer surfaces 37, 38and the system described is merely one commercially acceptablearrangemerit due to its simplicity and low initial cost. It can be seenthat the surface temperature setting at the two spaced points identifiedby the two spaced banks of themocouples on each platen are based onapproximate temperature values in accordance with the spacing andcapacity of the unit heaters but are sufficiently accurate to give theresults indicated in the graph of Figure 4. Greater refinement may bemade, however, if desired in the temperature control without departingfrom the scope of the invention. For instance, as previously discussed,each of the unit heaters may be individually controlled. Furthermore,the recess 41 may be omitted from the platen by the use of a differentoperating linkage and additional unit heaters may be added in thiscentral location to alter the heating conditions in the device 16.

If desired, transverse bores 94 may be provided in the platens adjacenteach end for accommodating the stem .of an indicating dial thermometer 6(Fig. 2). By means of these thermometers 96 any unusual temperaturechange in the platens during operation such as might occur as a resultof changing physical conditions or the like is readily visible to theoperator as he need only refer to the thermometer dial for periodicchecks of the running temperature conditions.

In the operation of the apparatus of Figure 1, the tow is advancedthrough the platens 17, 18 with the platens heat transfer surfaces 37,38 in contact with each side of the laterally spread tow. As the tow,which is initially at or close to room temperature, moves through theheating device 16, it is heated rapidly by the relatively large heatersat the rear end of the platens. This rapid heating quickly brings thetow to a softened condition at a predetermined stretching temperatureand in a uniform manner as a result of the transversely extendingposition of the heaters. Furthermore, the tow has moved only a shortdistance into the heating device (approximtely 5 inches in the specificembodiment) before this stretching temperature is reached as shown inthe graph of Figure 4. For instance, this stretching temperature may beapproximately 230 degree F. and it is maintained along the remainingportion of the tow within the platens under the sensing and controllingaction of the previously adjusted controllers 71, 72, 79 and 81.

The transversely extending heaters maintain a substantially uniformtemperature across the laterally spread tow to eliminate the highlyundesirable cold spots common to previous constructions. As the niprolls 2.1, 22 are rotated at a relatively faster speed than the niprolls, 13, 14 in accordance with the stretch ratio desired, the towemerges from the heating device 16 in the properly stretched conditionand proceeds in the above described manner through the remainingelements of the apparatus of Figure 1.

It can be seen through the novel construction of the heating device 16that the tow 11 may be brought quickly to a stretching temperature andmaintained at such temperature for a sufficient length so that asuitable length of tow is softened for the stretching operation.Furthermore, softening is uniform laterally across the tow andstretching under such ideal conditions means yarn fly is held to aminimum and filament breakage within the heating device is materiallyreduced. Another outstanding feature of the invention is the control ofthe physical characteristics of tow processed in the associatedapparatus afforded by the accurate stretching temperature control. Forinstance, it has been found that when the stretching temperature isincreased yarn shrinkage is decreased proportionally and as greaterstretch radios are permitted without affecting the amount of yarn fly,the tensile strength can be correspondingly increased at any given platetemperature. This extensive processing control means that filaments ofhighly sensitive synthetic material may now be processed and tailored tocustomer specification for any end fabric application.

While there has been described what at present is considered to be thepreferred embodiment of the invention, it will be understood by thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention and therefore it is the aimof the appended claims to cover all such changes and modifications asfall within the true spirit and scope of the invention.

Having thus described the invention, what is claimed 1s:

1. An improvement in apparatus for converting continuous filament towinto a tow of staple fiber comprising, in combination, a pair of spacedheating platens composed of a material of high heat conductivity, aheating surface on each of said platens, said platens arranged to bepositioned with said heating surfaces in substantially parallelrelationship, means to advance said tow through said platens in heattransfer relationship with said heating surfaces, a plurality ofelectrically operated heaters selectively spaced internally of saidplatens in the direction of tow movement with the axis of said heaterslying substantially at degrees to said direction, said heaters adjacentthe tow entrance end of said platens of relatively large capacity so asto bring said tow quickly to a predetermined stretching temperature,said heaters remote from said tow entrance end acting to maintain saidtow at the stetching temperature throughout the major portion of itslength within the platens, and means for controlling the energization ofsaid heating means in accordance with the temperature of said heatingsurfaces.

2. An improvement in accordance with claim 1 wherein said platens arecomposed of aluminum.

. An improvement in apparatus for converting continuous filament towinto a tow of staple fiber comprising, in combination, a pair of spacedheating platens composed of a material of high heat conductivity, aheating surface on each of said platens, said platens arranged to bepositioned with said heating surfaces in substantially parallelrelationship, means to advance said tow through said platens in heattransfer relationship with said heating surfaces, a plurality ofelectrically operated heaters selectively spaced internally of saidplatens in the direction of tow movement with the axis of said heaterslying substantially at 90 to said direction, said heaters being arrangedin a longitudinally spaced bank adjacent each end of said platens withsaid bank adjacent the tow entrance end of said platens includingheaters of relatively large capacity so as to bring said tow quickly toa predetermined stretching temperature, said heaters in the other bankacting to maintain said tow at a stretching temperature throughout themajor portion of its length within the platens, means for controllingthe energization of said heating means including a plurality ofthermocouples spaced transversely of said platens adjacent each of saidheater banks for sensing the temperature of said heating surfaces.

4. An improvement in accordance with claim 3 wherein said heaters arearranged in banks of three with said bank adjacent the tow entrance endof said platens including two heaters of relatively large capacity.

5. An improvement in apparatus for converting continuous filament towinto a tow of staple fiber comprising, in combination, a pair of spacedheating platens, a heating surface on each of said platens, said platensarranged to be positioned with said heating surfaces in substantialparallel relationship, means to advance said tow through said platens inheat transfer relationship with said heating surfaces, means associatedwith each of said platens for heating said surfaces, said heating meansextending substantially degrees to the direction of tow movement, andmeans for controlling the energization of said heating means inaccordance with the temperature of said heating surfaces to supply heatat a predetermined rate to portions of said tow advancing through saidplatens and bring said tow to a stretching temperature, said means forcontrolling energization of said heating means being regulated to supplyheat to said tow at a relatively greater rate adjacent the end of saidplatens at which said tow enters so as to maintain the tow at saidstretching temperature throughout the major portion of its traversethrough said platens.

6. An improvement in accordance with claim 5 wherein said platens arecomposed of aluminum.

7. An improvement in accordance with claim 3 wherein said platens arecomposed of aluminum.

References Cited in the file of this patent UNITED STATES PATENTS2,075,726 Kamerer Mar. 30, 1937 2,394,540 Finzel Feb. 12, 1946 2,456,384Conaway Dec. 14, 1948 2,504,440 Miess Apr. 18, 1950 2,748,426 Wyatt June5, 1956

